1. Field of Invention
This invention relates to a circuit with multiple remote sensors that detect excessive water in liquid form or in frozen form. More specifically, it relates to a circuit with multiple sensors that detect excess levels of accumulated moisture in liquid or frozen form and activates a control switch to disengage the associated system. It is most specifically related to the control of excess accumulated moisture in liquid or frozen form in air conditioning refrigerant systems.
2. Description of Related Art
Referring first to FIG. 1, a typical air refrigerant system 24 consists of a compressor 10, a compressor valve 10a, a valve chamber 10b, a condenser 13, condensing coil 12, a liquid storage vessel 14, a throttling valve 16, an evaporator 18, and a cooling coil 22, connected by a suitable conduit 20. The refrigerant, stored in the liquid storage vessel 14 is a liquid which partly vaporizes and cools as it passes through the throttling valve 16. Among the common refrigerants are ammonia, sulphur dioxide and various halides of methane and ethane. The refrigerant most often used in air refrigerant systems 24 is chlorodifluoromethane, commonly referred to as Freon.TM.. Nearly constant pressures are maintained on either side of the throttling valve 16 by means of the compressor 10. The mixed liquid and vapor entering the evaporator 18 is colder than the near-surround. Thus, the mixed liquid and vapor absorbs heat from the interior of the refrigerator box or cold room and completely vaporizes. The vapor is then forced into the compressor 10, where its temperature and pressure are increased as a result of the compression. The compressed vapor then pours into the condenser 13, where it cools down and liquifies as the heat is transferred to outside air, water, or other fluid medium in the condensing coils 12.
In such air refrigerant systems 24 the evaporator 18 often lowers the air temperature below the dew point. As a result, moisture will condense on the cooling coil 22. For this reason, air refrigerant systems 24 are also provided with an overflow pan (not yet shown) for collecting moisture condensed on the cooling coil 22. The moisture collected by the overflow pan is then removed by an overflow line (not yet shown). However, dust and other airborne debris as well as algae may accumulate in the overflow pan and eventually plug the overflow line. In other circumstances, a sewer line (not shown) to which the overflow line is typically connected, may become plugged due to causes unrelated to the air refrigerant system 24 itself In any event, whenever the overflow pan is prevented from draining, the level of condensation in the overflow pan will steadily increase until the pan overflows, thereby causing water damage to the air refrigerant system 24 and its environment.
In an effort to resolve this problem, manufacturers of air refrigerant systems built a secondary overflow pan connected to a separate overflow line beneath the primary overflow pan. When the overflow line of the primary overflow pan becomes plugged, condensation will collect in the primary overflow pan until filled. The overflow would then spill over into the secondary overflow pan and drain by way of the overflow line of the secondary overflow pan. While such secondary overflow drainage systems made condensation overflows less likely, they offered no protection from overflows if both drainage systems were blocked. It is not uncommon for both the primary and secondary overflow pan to be plugged at the same time taking into consideration that the same condition that plugs one will usually plug the other. As a result, overflow protection systems often include a switching system to turn the air refrigerant system off in the presence of condensation overflow conditions.
Referring next to FIG. 2, a float actuated switching system for an air refrigerant system 24 may now be seen. U.S. Pat. No. 3,473,553 Thomas Collins Oct. 21, 1969. The air refrigerant system in FIG. 2 consists of a load, which may include the air refrigerant system of FIG. 1, #24 connected to a relay via a temperature activated relay (not yet shown) of conventional design, connected in series to a low voltage electrical transformer (not yet shown) using electrical connectors 28. The overflow pan, which may either be a primary overflow pan (not yet shown) or a secondary overflow pan 30, collects condensating liquid which drains via the overflow line 32. A float actuated switch 34 includes a float 36 positioned in the secondary overflow pan 30 and an electrical contact 38 balanced by a pivot or fulcrum 40. When the level of condensation in the secondary overflow pan 30 is low, the electrical contact 38 is engaged with the contacts 28a and 28b of the air refrigerant system 24, thereby permitting power to flow through the (load) air refrigerant system 24, thus maintaining the air refrigerant system 24 in an ON condition. In the event that the overflow line 32 becomes plugged, condensation will begin to accumulate in the secondary overflow pan 30, raising the level of the float 36. When the float 36 has been raised to a specified height, the electrical contact 38 will disengage from the contacts 28a and 28b, thereby disconnecting the (load) air refrigerant system 24 from the AC source 26 and turning the air refrigerant system OFF. Unfortunately, due to space limitations imposed during the manufacture of air refrigerant systems 24, float actuated switches 34 such as the one described herein are often too large to fit into the primary overflow pan (not yet shown) which is positioned within the cooling coil housing (not yet shown). In addition, air currents within the cooling coil housing (not yet shown) could easily displace the float 36, thereby resulting in erroneous switching. Finally, float activated switches 34 are particularly undesirable when liquid is draining at a rate just slightly less than the rate at which condensation is being collected by the secondary overflow pan 30. For example, the overflow line 32 may be partially plugged such that drainage of the accumulated condensation from the secondary overflow pan 30 is occurring at a lightly below normal rate while condensation continues to accumulate at a normal rate. Under these circumstances, the float actuated 34 switch could rapidly oscillate between the ON and OFF states, a condition which may result in damage to the air refrigerant system 24 and allowing overflow into its environment.
Another attempt at solving this problem was invented by John T. Thorngren, U.S. Pat. No. 5,196,729 Mar. 23, 1993. Referring now to FIG. 3. This invention is a control switch 48, that mounts to the sidewall 45 of the secondary overflow pan 30 by mounting means such as a cylindrical clamp 46 fitted into a slitted sidewall 46a and having two liquid detecting probes 54 and 56 extending outward which, upon detection of liquid, disconnects the air refrigerant system 24. This invention has several limitations and deficiencies as discussed in the following paragraphs.
While containment of condensation water droplets is a major problem, and the one that has been addressed to this point, there is yet another frequent problem. Specifically, ice. When compressed Freon.TM. passes through the throttling valve 16, it causes a phase change from liquid to gas. The Freon.TM. is cold due to the phase change and is passed through cooling coils 22 that act as a heat exchanger removing heat from air passing over the cooling coils 22, If the Freon.TM. temperature is lower than the dew point of the air, moisture condenses on the cooling coil 22. If the Freon.TM. temperature is lower than 32 degrees Fahrenheit, frequently caused by various malfunctions in the system, the accumulated moisture that has formed on the cooling coils 22 will freeze, thus forming ice on the cooling coils 22 and eventually damaging the system to the point that the ice will bend the cooling coils 22, causing a puncture in the tubing and releasing the Freon.TM., thus causing the compressor 10 to malfunction and stop operating. Applicant has personally observed ice to be, in some cases, throughout the entire cooling coil 22 equal in size to a block of ice approximately 9".times.22".times.36" or larger, before the compressor 10 malfunctions due to excessive stress on the compressors valve 10a due to improper mix of Freon.TM. vapors now being fed into the valve chamber 10b. When the compressor 10 shuts off due to the damaged valve 10a, the ice that had previously formed begins to rapidly melt causing water to leak, first into the primary overflow pan (not yet shown) then spilling over into the secondary overflow pan 30 in larger amounts and at a faster rate than the normal condensation. This melted ice, or water, causes overflow, even if both primary and secondary overflow pans are functioning properly, because the blower (not shown), which would still be working, sends forced air into the path of the melting ice causing constant sprays throughout the attic or space where the air refrigerant system was installed. Additionally, the rate at which the ice would melt, due to the natural temperature of the area of installation, would be overwhelming to the overflow pans, both primary (not yet shown) and secondary 30. Considering most installations of air refrigerant systems 24 for air conditioning purposes are installed on top of a building, as in commercial applications, or in an attic or overhead space as in residential applications, water from the melted ice causes damage from flooding, to the floor of the area of installation and eventually damages the ceiling of the room beneath. Undetected, this condition would, in multiple story buildings, continue downward damaging floors, ceilings and contents, through several stories. Thorngren's invention has no capability to monitor ice.
Additionally, Thorngren's control switch 48 contains the circuit (not shown) and the liquid detecting probes 54 & 56. This requires it to be of a size that prohibits installation in small, tight areas such as the space allowed by the design of air refrigerant systems 24 between the cooling coil 22 and the primary overflow pan (not yet shown). Therefore his control switch 48 would be installed only in the secondary overflow pan 30 where more space is afforded by the designers of the air refrigerant systems.
Furthermore, the sidewall 45 of the, usually metal, secondary overflow pan 30 must be cut to create a slit to accommodate the control switch 48 to be wrapped by the cylindrical clamp 46. This necessary slit in the sidewall 45 of the secondary overflow pan 30 could allow the water to leak out of the secondary overflow pan 30 before it reaches his horizontally installed control switch 48. In Thorngren's invention, the primary overflow pan (not yet shown) must be in an overflow condition and the secondary overflow pan 30 must be in a near overflow condition before this invention initiates.
It is also noted that Thorngren's control switch 48 is attached to the top edge of the secondary overflow pan 30 at a position, very near the top edge of the secondary overflow pan 30 with a cylindrical clamp 46. Condensation overflow pans vary greatly in different types of installations, depending upon the size of the air conditioning system installed. Commercial systems, which normally have no secondary overflow pan 30, will require different levels of detection due to varying sizes of primary overflow pans (not yet shown). To be efficient in early detection and quickly disengaging the system to eliminate damage related to overflow conditions, the location of the control switch 48 within the overflow pans would need to be perpendicularly adjustable The invention described does not include any means for such adjustment.
It is further observed that Thorngren's invention, having the circuit (not shown) and probes 54 & 56 inside a single control switch, 48 could not be used in multiple stage systems that have 2 or 3 separate cooling coils which would require multiple remote detection.